A common problem encountered when formulating liquid or cream products which are meant to deliver a volatile material either as their primary function (e.g. perfumes or insecticides) or as their secondary function (e.g. detergents) is to have a sustained release of the volatile material over a long period of time. Another problem is that if the volatile material is a composition formed by several components of different volatility, the more volatile materials tend to evaporate at a much faster rate than the less volatile ones and therefore the release is not balanced, and the delivered volatile composition changes with time.
Prior art attempts to solve this problem are generally based on the use of microcapsules: the volatile material is enclosed in a capsule of polymeric material which is dispersed into the liquid or cream product, said capsules break, dissolve or melt upon product usage due to the intervention of the user. An approach of this type is described e.g. in WO 02/074430 from Quest. This solution is effective in that it allows the delivery of the full perfume bouquet when the capsules are broken or dissolved. On the other hand, the use of capsules for volatile material delivery presents several problems: capsules are difficult to stably disperse in liquids; they tend to leak in the presence of surfactants in the products where they are dispersed, and also they might not break when required thus making it difficult to have a sustained and controlled volatile material release.
EP1318191 from Buck Chemie describes viscous pastes which comprise EO-PO block copolymers and a perfume which are dispersed into water. These compositions still are not satisfactory as they do not have in general a good compatibility with a wide range of volatile materials, particularly perfumes, thus resulting in a lack of flexibility in releasing complex perfumes. Another problem of the compositions described herein is that they are effective when used as such, but when they are incorporated e.g. in a water based product, the copolymers, having strong surfactant properties, tend to form micellar structures in the solution, to interact with the surfactant system, thus dispersing the perfume in the product and losing effectiveness as perfume release control.
Therefore there is a need for a stable system for controlled, balanced and sustained release of volatile materials which can be effectively incorporated in liquid or cream products, in particular cleaning detergent products and personal care products.
The compositions of the present invention can be easily dispersed in liquid or cream products and also allow a balanced release of all components of the volatile material over a long period of time. When the volatile material is a perfume, which is typically composed of many components of different volatility, an additional advantage of the present invention is that, avoiding separation of the components based on their different volatilities, it allows the sustained and balanced delivery of the full perfume character for a long time.